The present disclosure relates to a solid-state image pickup element and an electronic device, particularly to a solid-state image pickup element and an electronic device which ensures stable overflow.
In general, a solid-state image pickup device such as a CMOS (Complementary Metal Oxide Semiconductor) image sensor or CCD (Charge Coupled Device) is widely used for a digital still camera, a digital video camera or the like. For example, incident light on the CMOS image sensor is photoelectrically converted by PD (Photodiode) included in a pixel. Then, a charge generated in PD is transferred to FD (Floating Diffusion) via a transfer transistor and converted by FD to a pixel signal of a level corresponding to an amount of received light and the pixel signal is read out.
In the past, a method of forming PD at a deeper portion of a silicon substrate below a pixel transistor, or a method of laminating PD in a depth direction are disclosed as methods for increasing a saturation charge amount of the solid-state image pickup element.
For example, a method of using a vertical transfer transistor having a channel direction perpendicular to a semiconductor substrate for improving readout performance of a charge from PD that is formed in a deep part of a silicon substrate is disclosed in Japanese Patent Laid-Open No. 2010-114274.
In general, an overflow drain is formed in a solid-state image pickup element as an overflow destination for inhibiting a charge stored in PD from overflowing in various directions to affect imaging property when light of high illumination is incident upon a solid-state image pickup element. The overflow drain is a type used with FD or a diffusion region set at a source voltage.